aw: Set enable/disable feature once

Comments

aw: Set enable/disable feature once
Previous implementation appended a new --enable-feature or
--disable-feature switch for every hard coded feature. Command line argv
turned out to be append only, even though there is a remove switch
method.
Change to a scoped class and append each at most only one.
Change-Id: Ic0243d69bf23038c17a31a76f32ff2a88505028c
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1526746
Commit-Queue: Bo <boliu@chromium.org>
Reviewed-by: Nate Fischer <ntfschr@chromium.org>
Cr-Commit-Position: refs/heads/master@{#641830}